This invention relates to bearings used to mount shafts for rotation in the bearing, and particularly relates to a pillow block bearing wherein the inner race ring of the bearing is locked to the shaft by circumferentially spaced set screws in the race ring which are threadably tightened on to the shaft.
Shafts mounted in pillow block bearings are conventionally of relatively soft steel. In fact, most shafting for pillow block bearings is of necessity rather long, and is most readily available in the soft form. If the shaft was hardened, it would be expensive and there would be a disadvantage to it for much of the holding power of the set screw locking depends upon a hard set screw deforming the shaft as the set screw is tightened to locking position on the shaft. When the hard steel set screw is tightened onto the shaft, the set screw deforms or raises burrs as the end of each set screw digs into the shaft. Although the burrs in one typical bearing size are generally in the order of 0.011 inch high, this is still a protuberance on the shaft and is in frictional contact with the bore of the inner race ring, for the latter normally fits rather closely to the surface of the shaft.
Other locking means than set screws have been employed for locking a pillow block bearing on a shaft but these are more expensive than multiple set screw locking, and the latter is the preferred structure for bearings particularly of the pillow block type.
Bearings, and sometimes shafts, wear in use and have to be replaced. The burrs are raised directly under the respective set screws and hence within the bore of the inner race ring, and they make it very difficult to slide the shaft and inner race ring relative to one another to separate them for replacing the bearing or shaft. Normally it is the bearing which has to be replaced, but for those installations where the shaft must be replaced the advantages of the present invention apply.
Inasmuch as set screw locking has been the most conventional means for locking a pillow block bearing on a shaft for as long as pillow block bearings have been used, the matter of burrs on the shaft is a long standing problem in the bearing art when bearing and shaft must be separated.